Chapter - 1
Laboratory Instruments and Techniques
1. What is the primary function of a common balance in a clinical laboratory?
A) To measure liquid volume.
B) To find out the mass of a substance by comparing it with known masses.
C) To determine specific gravity.
D) To measure reaction time.
Correct Answer: B
2. For which purpose are Physical balances (open two-pan type) generally used?
A) Preparation of standard solutions.
B) Weighing substances requiring accuracy up to 0.001 mg.
C) Preparation of quantitative reagents.
D) Weighing out substances where great accuracy is not required, such as preparation of qualitative reagents.
Correct Answer: D
3. What is the typical weighing range that can be obtained on a two-pan analytical balance?
A) 0.001 mg to 0.01 mg.
B) 0.1 mg to 10 g.
C) 0.001 to 100 g.
D) 100 g to 1000 g.
Correct Answer: C
4. Which type of balance is considered the most sensitive, with weighing accuracy obtainable up to 0.001 mg?
A) Physical balance.
B) Two-pan analytical balance.
C) Monopan balance.
D) Electrical balance based on null detector.
Correct Answer: C
5. Mono-pan balances work on which fundamental principle?
A) Comparison of masses using a beam.
B) Substitution of weights.
C) Measurement of electrical current proportional to mass.
D) Calculation of RCF.
Correct Answer: B
6. According to the care and maintenance instructions, what precaution should be taken regarding substances placed directly on the balance pan?
A) The substance should be weighed hot for better accuracy.
B) Never weigh the substance by placing it directly on the pan; use a butter paper or watch-glass.
C) The substance should only be weighed directly if it is a liquid.
D) The cabinet should be kept open while weighing.
Correct Answer: B
7. Which component is found in a two-pan analytical balance but is not listed as a major part of a mono-pan balance?
A) A beam.
B) Stirrups.
C) Scale Pans (compared to A pan in mono-pan).
D) Ivory scale.
Correct Answer: D
8. In the weighing procedure for a two-pan analytical balance, where should the object to be weighed be placed?
A) In the right pan.
B) In the left pan.
C) On the central vertical pillar.
D) On the rigid supports.
Correct Answer: B
9. Electrical balances employ which mechanism to return the system to equilibrium after a weight is placed on the pan?
A) Standard calibrated weights.
B) Fixed constant counterweights.
C) Electromagnetic restoring forces.
D) Adjusting the screw nuts at the end of the beam.
Correct Answer: C
10. The performance of an analytical balance is judged by which three criteria?
A) Weighing range, speed, and cost-effectiveness.
B) Sensitivity, precision, and accuracy.
C) Knife edges, scale pans, and pointer swing.
D) Null detection, feedback loop, and digital readout.
Correct Answer: B
Hot Plate, Magnetic Stirrer, Hot Air Oven, and Incubators
11. What is the instrument used primarily for the fast mixing of solutes in a solution, utilizing a rotating magnetic field?
A) Hot air oven.
B) Centrifuge.
C) Magnetic stirrer.
D) Analytical balance.
Correct Answer: C
12. The working principle of a hot plate and magnetic stirrer is based on the production of:
A) Thermal gradients to induce convection.
B) Rotating magnetic fields in a metal plate.
C) Centrifugal force.
D) Electrical current conversion to light.
Correct Answer: B
13. Which of the following is listed as a primary use for a Hot Air Oven?
A) Growing microorganisms on culture media.
B) Separation of serum from red blood cells.
C) Dry sterilization.
D) Carrying out chemical reactions at specific temperatures.
Correct Answer: C
14. What component is used to control the temperature in both a hot air oven and an incubator?
A) A tachometer.
B) A galvanometer.
C) A thermostat.
D) A central knife edge.
Correct Answer: C
15. What is the temperature range typically recorded by the thermometer in a Hot Air Oven?
A) 0°C to 100°C.
B) 30°C to 80°C.
C) 40°C to 300°C.
D) 300°C to 500°C.
Correct Answer: C
16. What is the range of temperature control for an Incubator?
A) 0°C to 100°C.
B) 30°C to 80°C.
C) 100°C to 300°C.
D) 800°C to 900°C.
Correct Answer: B
17. What is an important application of Incubators listed in the sources?
A) Preparation of primary standards.
B) Growing microorganisms on various culture media.
C) Loosening a blood clot.
D) Determining the RCF.
Correct Answer: B
18. What is a Muffle furnace a type of, and what high temperature range can it achieve?
A) A type of centrifuge, achieving up to 10,000 RPM.
B) A type of water bath, achieving up to 100°C.
C) A type of hot air oven, achieving temperatures up to 800–900°C.
D) A type of photometer, achieving 400 nm to 760 nm.
Correct Answer: C
19. In the preparation of anticoagulant bulbs for blood sugar determination, what is used to prevent the conversion of blood glucose to lactic acid (glycolysis)?
A) Sodium carbonate.
B) Copper sulfate.
C) Sodium fluoride.
D) Sodium citrate.
Correct Answer: C
20. What material constitutes a thermostat, used for temperature control?
A) A plastic paddle.
B) A fixed constant counterweight.
C) A bimetallic strip made of two strips of different metals rivetted together.
D) A graphite brush.
Correct Answer: C
Centrifuges
21. What are the two general types of centrifuges used in laboratories, categorized by their rotor design?
A) High speed and ultracentrifuge types.
B) Physical and analytical types.
C) Swing out head type (horizontal rotor) and Angle head type (fixed angle rotor).
D) Electrical and substitution types.
Correct Answer: C
22. Why are angle head rotors able to attain much higher speeds than swing out head rotors (typically limited to 5000 RPM)?
A) They use a stronger motor drive assembly.
B) They are positioned rigidly at a fixed angle, resulting in very low friction of air.
C) They generate less electrical noise.
D) They operate on the principle of substitution of weights.
Correct Answer: B
23. Centrifuges capable of producing speeds up to 100,000 RPM and RCF values up to 500,000 x g are referred to as:
A) High speed centrifuges.
B) Preparative centrifuges.
C) Ultracentrifuges.
D) Angle head centrifuges.
Correct Answer: C
24. Which expression of force is considered a better, quantitative measure of the force generated by a centrifuge?
A) RPM (Revolutions Per Minute).
B) RCF (Relative Centrifugal Force).
C) R (Radius from the center of rotation).
D) Standard deviation.
Correct Answer: B
25. The mathematical formula for Relative Centrifugal Force (RCF) includes which key variables?
A) Viscosity and specific gravity.
B) Length of radius (R) and the speed of rotation (RPM).
C) Gravitational force and particle size.
D) Volumetric capacity and rotation speed.
Correct Answer: B
26. What component provides electrical contact to the commutator (rotor) in a centrifuge, and what material is used for this contact?
A) The speed control knob.
B) A timer.
C) Graphite brushes.
D) Rubber pads (cushions).
Correct Answer: C
27. The working of a centrifuge is based on the principle of centrifugal force, which acts on a substance in circular motion, towards the:
A) Center of rotation.
B) Periphery.
C) Vertical axis.
D) Top of the tube.
Correct Answer: B
28. Which of the following is listed as a primary factor that governs the speed of centrifugation?
A) The acceleration due to gravity (g).
B) The length of radius (measured from the center of rotation to the inside bottom of the tube).
C) The temperature of the chamber.
D) The color of the specimen.
Correct Answer: B
29. For the separation of serum or plasma from red blood cells, what instrument is mainly used in a laboratory?
A) Hot air oven.
B) Centrifuge.
C) pH meter.
D) Reflectance photometer.
Correct Answer: B
30. Before centrifugation, what essential step must be performed to ensure proper operation and prevent excessive vibration?
A) The centrifuge tubes and cups should be chilled.
B) The motor drive assembly must be lubricated.
C) The centrifuge tubes and the cups or tubes of the centrifuge should be balanced properly.
D) The timer must be set to 10 minutes.
Correct Answer: C
31. If the calibrations furnished on the speed control of a centrifuge should never be taken as accurate indicators of speed, what do these calibrations indicate?
A) Only relative voltage increments.
B) Accurate RCF values.
C) Absolute RPM readings.
D) The friction resistance.
Correct Answer: A
32. Which factors resist the speed of centrifugation?
A) Air resistance and turbulence, brush friction, and electrical inefficiency of the centrifuge itself.
B) Radius of rotation and total mass.
C) RCF and RPM.
D) The presence of graphite brushes.
Correct Answer: A
33. When performing the separation of plasma from anticoagulated blood, what centrifugation parameters were used in the described procedure?
A) 5000 RPM for 5 minutes.
B) 1500 RPM for 10 minutes.
C) 15,000 RPM for 10 minutes.
D) 100,000 RPM for 30 minutes.
Correct Answer: C
34. A High speed centrifuge is useful for research work and can achieve a maximum speed up to:
A) 5000 RPM.
B) 10,000 RPM.
C) 20,000 RPM.
D) 100,000 RPM.
Correct Answer: C
35. How often should RPM calibration of a centrifuge be checked using an external device like a tachometer?
A) Annually.
B) The values obtained should agree within 5% of those from a built-in tachometer.
C) Only when the RCF formula is applied.
D) Before every use.
Correct Answer: B
Colorimetry and Photometry
36. Analytical procedures based upon the direct measure of color intensity in terms of light absorption at specific wavelengths are known as:
A) Immunonephelometric procedures.
B) Photometric procedures.
C) Chemiluminescence.
D) Rate of reaction methods.
Correct Answer: B
37. What is the unit used to express wavelength in colorimetry and photometry?
A) Angstrom (Å).
B) Meters (m).
C) Nanometers (nm).
D) Centimeters (cm).
Correct Answer: C
38. Sunlight is a type of radiant energy that comprises which parts of the spectrum?
A) Ultraviolet (UV), visible, and infrared light.
B) Only visible light.
C) Only UV light (below 380 nm).
D) Only infrared light (above 760 nm).
Correct Answer: A
39. What is the definition of Optical Density (O.D.) in relation to percent transmittance (T)?
A) O.D. = log (%T).
B) O.D. = 2 - log T.
C) O.D. = T / C.
D) O.D. = (RPM) * R.
Correct Answer: B
40. What is a Monochromator defined as?
A) Any system that measures electrical current.
B) Any system or component that will transmit monochromatic light (light of single wavelength).
C) A device that holds the solution.
D) A mechanism that converts radiant energy to electrical energy.
Correct Answer: B
41. In the case of a spectrophotometer, what devices are used as a monochromator to transmit single wavelength?
A) A filter.
B) A prism or diffraction with a slit.
C) A light source bulb.
D) A photocell.
Correct Answer: B
42. A tungsten lamp primarily emits a continuous spectrum of light in which range?
A) UV range (200 nm to 400 nm).
B) Visible range (400 to 760 nm).
C) Infrared range (above 760 nm).
D) Halogen range (20-900 mm).
Correct Answer: B
43. What is the preferred width/path of light for a cuvette?
A) 0.5 cm.
B) 1 cm.
C) 2 cm.
D) 5 cm.
Correct Answer: B
44. Which photodetectors generate an electrical current when light transmitted by a solution falls on them, utilizing light sensitive material such as selenium or cuprous oxide?
A) Monochromators.
B) Cuvettes.
C) Photocells (Barrier layer cells).
D) Galvanometers.
Correct Answer: C
45. A blue solution appears blue because, when white light passes through it:
A) It absorbs all colors except blue.
B) It absorbs a large proportion of blue light.
C) A large proportion of blue light will be transmitted, and other parts (green, yellow, red, etc.) are absorbed.
D) It transmits yellow and green light.
Correct Answer: C
46. What is the function of a Blank solution in a photometric procedure?
A) To maximize absorbance of the test sample.
B) To set the meter of the instrument to 100% T or zero absorbance.
C) To act as a primary standard.
D) To increase the sensitivity of the instrument.
Correct Answer: B
47. Which components are included in a basic photometer?
A) Light source, lens (condenser), filter, cuvette, galvanometer.
B) Light source, prism, cuvette, photomultiplier tube.
C) Halogen lamp, diffraction grating, flow cell.
D) Thermostat, stirring paddle, speed control.
Correct Answer: A
48. What fundamental principle states that the optical density of a solution is directly proportional to the concentration of the solution?
A) Lambert's law.
B) Stoke's law.
C) Beer's law.
D) Faraday's law.
Correct Answer: C
49. Lambert's law states that the optical density of a colored solution is directly proportional to:
A) The concentration of the solution.
B) The path of light (diameter of the cuvette).
C) The wavelength of the light.
D) The temperature of the solution.
Correct Answer: B
50. If the diameter of the cuvette is doubled, according to Lambert's law, what happens to the Optical Density (O.D.)?
A) It is halved.
B) It remains the same.
C) It is doubled.
D) It is quadrupled.
Correct Answer: C
51. What is the numerical relationship between 29% Transmittance (%T) and Optical Density (O.D.) according to the provided table?
A) 0.201 O.D.
B) 0.538 O.D..
C) 0.602 O.D.
D) 0.292 O.D.
Correct Answer: B
52. What indicates the presence of interfering ions such as sodium, calcium, and chlorides during the standardization of distilled (or deionized) water using silver nitrate reagent?
A) Absence of color change.
B) Appearance of turbidity.
C) An increase in pH.
D) A decrease in freezing point.
Correct Answer: B
53. Filter photometers are generally less expensive than spectrophotometers, but are satisfactory for routine analytical purposes only in which spectral region?
A) Ultraviolet region.
B) Infrared region.
C) Visible region.
D) Microwave region.
Correct Answer: C
54. The width of the spectral region transmitted by filters in photometers is typically:
A) Monochromatic (single wavelength).
B) Narrow band (4 to 20 nm).
C) Wide range (80-100 nm).
D) Exactly 1.0 nm.
Correct Answer: B
55. Spectrophotometers use prisms or diffraction gratings as monochromators. These devices separate wavelengths by which physical processes, respectively?
A) Diffusion or reflection.
B) Refraction or diffraction.
C) Absorption or transmittance.
D) Filtration or interference.
Correct Answer: B
56. What material must be used for cuvettes in UV-determinations because glass absorbs UV light?
A) Standard plastic.
B) Borosilicate glass.
C) Rectangular quartz thermocuvettes.
D) Round tube type cuvettes.
Correct Answer: C
57. Phototubes are constructed of a negatively charged cathode coated with a photo emissive substance. What is an advantage of phototubes over photovoltaic cells (photocells)?
A) They are less expensive.
B) They are simpler to operate.
C) They may be obtained with wide ultraviolet and infrared sensitivity.
D) They do not require external power.
Correct Answer: C
58. What is the Photometric range of the Spectronic '20' spectrophotometer in terms of Absorbance (A)?
A) 0% T to 100% T.
B) 0 A to 2.0 A.
C) 2.5 nm to 20 nm.
D) 340 nm to 950 nm.
Correct Answer: B
59. What should be done to a single cell photometer for 10 minutes before taking readings?
A) Place the colored solution in the cuvette.
B) Turn on and warm up the main light source.
C) Adjust the galvanometric pointer to zero.
D) Calculate the unknown concentration.
Correct Answer: B
60. When plotting photometric data for standardization, which graphical presentation indicates a straight line passing through the origin, establishing agreement with Beer's law?
A) %T (y axis) against concentrations (X axis).
B) O.D. (y axis) against concentrations (X axis).
C) O.D. (y axis) against wavelength (X axis).
D) %T (y axis) against O.D. (X axis).
Correct Answer: B
61. For the determination of an unknown concentration of a potassium dichromate solution (yellow colored), which filter/wavelength is suggested in Experiment No.: 4.8?
A) Green filter (525 nm).
B) Yellow filter (575 nm).
C) Violet filter (420 nm).
D) Red filter (660 nm).
Correct Answer: C
62. For a blue colored solution, what is the complementary filter recommended?
A) Blue.
B) Green.
C) Yellow or Red.
D) Purple.
Correct Answer: C
63. From an analytical point of view, what is the most satisfactory wavelength for photometric measurement?
A) The one that provides maximum sensitivity.
B) The one that shows agreement with Beer's law over a wide range of concentrations and permits this range to be read within the accurate region of the photometer scale (0.05 to 0.8 O.D.).
C) The one that uses a complementary filter regardless of O.D. readings.
D) The one corresponding to infrared light.
Correct Answer: B
64. What happens when the concentration of a substance in solution is increased, regarding light absorption?
A) Light absorption decreases at all wavelengths.
B) Light absorption remains constant regardless of wavelength.
C) There is usually increased light absorption at all wavelengths where any light is absorbed.
D) Only the visible spectrum is affected.
Correct Answer: C
65. What is the typical effect of fluctuation in the main electric supply on readings taken with a single cell photometer?
A) Readings remain stable due to compensation.
B) Readings may vary according to the electrical fluctuations.
C) The instrument automatically switches to battery power.
D) The photodetector system is nullified.
Correct Answer: B
66. What mechanism in a double cell photometer nullifies the effects of fluctuations in the main electric supply or unstable light source?
A) Use of a halogen lamp.
B) Two closely matched selenium cells balanced against each other in a balanced circuit.
C) Manual operation by the user.
D) Using a prism instead of a filter.
Correct Answer: B
67. What characteristic is used in determining the quality of light?
A) Molar extinction coefficient.
B) Wavelength, which is the distance between the crests of the waves.
C) Optical density.
D) Transmittance ratio.
Correct Answer: B
68. What are the photodetectors made up of in the most common barrier layer cells?
A) Glass and quartz.
B) Iron back plate coated with a layer of crystalline selenium or cadmium on one surface.
C) Deuterium discharge material.
D) Polypropylene membrane.
Correct Answer: B
69. What is the primary function of a galvanometer in photometers and spectrophotometers?
A) To generate monochromatic light.
B) To focus light beams.
C) To detect and measure electrical current produced by the photodetectors.
D) To amplify the signal through a cascade of electrons.
Correct Answer: C
70. For work in the ultraviolet region (UV), what type of light source is useful, compared to the ordinary tungsten lamp?
A) A fixed constant counterweight.
B) A tungsten lamp operated at a higher voltage.
C) A high pressure hydrogen (or deuterium) discharge lamp, or a halogen lamp.
D) A muffle furnace.
Correct Answer: C
76. The detection of glucose, urea, uric acid, cholesterol, triglycerides, etc., by enzymatic methods often falls under which category of assay methodology?
A) Qualitative tests.
B) Mono-step methods.
C) Multi-step methods.
D) Radioimmunoassays.
Correct Answer: B
77. What is the purpose of including a reagent blank with each batch of determinations, particularly if the reagent is colored?
A) To act as a secondary standard.
B) To eliminate the intensity of the reagent from the intensity of the end product.
C) To check for electrical fluctuations.
D) To perform linearity checks.
Correct Answer: B
78. Why is a separate sample blank required if a specimen is colored (e.g., hemolyzed, icteric, or lipemic)?
A) To increase the reaction time.
B) To correct the 'Test' reading by subtracting the specimen blank reading.
C) To confirm the specificity of the reaction.
D) To measure the light path accurately.
Correct Answer: B
79. The Folin-Wu blood sugar method is classified as what type of quantitative method?
A) Mono-step method.
B) Enzymatic method.
C) Multi-step method.
D) UV-kinetic method.
Correct Answer: C
80. A key drawback of the Folin-Wu method for glucose determination is that it is not accurate because:
A) It requires centrifugation.
B) Non-glucose reducing substances such as glutathione, ascorbic acid, and uric acid also reduce cupric ions.
C) It requires heating.
D) It can only be performed on ultracentrifuges.
Correct Answer: B
81. What is the reaction type, wavelength, and filter used for the determination of plasma glucose by the Glucose-Oxidase/Peroxidase (GOD/POD) method described?
A) UV-kinetic, 340 nm, no filter.
B) End-point, 520 nm, green filter.
C) Multi-step, 420 nm, violet filter.
D) Rate of reaction, 405 nm, yellow filter.
Correct Answer: B
82. When assessing a quantitative method, what criteria must it meet regarding accuracy?
A) It must produce the same value for replicate measurement.
B) It must give a correct result.
C) It must measure low concentration of the analyte.
D) It must not be subject to interference by other substances.
Correct Answer: B
83. Precision of an instrument is expressed as:
A) The scale division deflection per mg.
B) The standard deviation of repetitive measurement of the same mass.
C) The ratio of scale response change to weight change.
D) The degree to which a curve approximates a straight line.
Correct Answer: B
84. Linearity, as defined by NCCLS, is the measure of the degree to which a curve approximates a:
A) Parabola.
B) Sine wave.
C) Straight line.
D) Hyperbolic curve.
Correct Answer: C
85. Under CLIA '88 mandates, how often must calibration verification or recalibration be verified for a procedure?
A) At least every six months or when a complete change of reagents is introduced.
B) Before every test.
C) Only when new instrumentation is purchased.
D) Annually.
Correct Answer: A
86. In the determination of linearity for the glucose oxidase method, up to what optical density (O.D.) was Beer's law obeyed in the example provided?
A) 0.06 O.D.
B) 0.24 O.D.
C) 0.6 O.D..
D) 0.8 O.D.
Correct Answer: C
87. In rate of reaction methods, the period of constant reaction rate where the rate depends only on enzyme concentration is known as:
A) First-order dependence.
B) Zero order rate of reaction.
C) Lag phase.
D) Enzyme denaturation phase.
Correct Answer: B
88. The determination of serum Creatinine via the visible kinetic method involves measuring the intensity of the yellow-red colored complex at 510 nm at two time points:
A) A₁ after 1 minute and A₂ after 3 minutes.
B) A₁ after 20 seconds and A₂ after 80 seconds.
C) A₀ (zero time) and A₁ after 5 minutes.
D) After the lag phase and after 10 minutes.
Correct Answer: B
89. Why are primary standards (purified enzyme) generally *not* used for enzyme determinations in end point reaction methods?
A) They are too sensitive.
B) They are extremely expensive and enzyme preparations are unstable.
C) They interfere with Beer's law.
D) They cannot be dissolved in buffer.
Correct Answer: B
90. In UV-Kinetic methods, which components absorb UV-light specifically at 340 nm?
A) ATP and ADP.
B) Glucose and gluconic acid.
C) NAD, NADH, NADP, and NADPH.
D) Paranitrophenyl phosphate.
Correct Answer: C
Fluorimetry, Reflectance Photometry, and Flame Photometry
91. What is the process called when excited electrons in molecules dissipate their excess vibrational energy as heat and reach the minimal vibrational energy level of the lowest excited state ($S_1$)?
A) Fluorescence.
B) Ground state transition.
C) Collision.
D) Quenching.
Correct Answer: C
92. What structural feature favors fluorescence in a molecule?
A) Electron withdrawing groups such as -NO₂.
B) Lack of resonance.
C) Rigidity in a molecule.
D) High temperature.
Correct Answer: C
93. In fluorescence, the intensity of fluorescence emission is directly proportional to the strength of the incident excitation source and what other factor?
A) Specific gravity.
B) The partition coefficient.
C) The quantum efficiency of fluorescence.
D) Viscosity of the solvent.
Correct Answer: C
94. What is the effect of high concentrations of the fluorescent species in solution?
A) Fluorescence intensity increases linearly.
B) Emitted fluorescence is dissipated by self-quenching.
C) Low temperature is required.
D) The measurement shifts to the infrared region.
Correct Answer: B
95. In Flame Photometry, which alkali metals are best suited for measurement due to their low ionization potentials?
A) Copper, Cadmium, Lead.
B) Sodium, potassium, lithium.
C) Iron, Magnesium, Zinc.
D) Nitrogen, Sulfur, Carbon.
Correct Answer: B
96. In Flame Photometry, what is the color produced by Potassium in the flame?
A) Yellow.
B) Violet.
C) Red.
D) Blue.
Correct Answer: B
97. Reflectance Photometry involves the measurement of light reflected from a surface. This principle is used in which clinical instruments?
A) Analytical balances.
B) Spectrophotometers.
C) Glucometers, dry-chemistry analyzers, and reflectance densitometers.
D) PCR equipment.
Correct Answer: C
98. Dry chemistry technology uses plastic strips with cellulose area impregnated with specific testing chemicals. When a specimen is placed on the reaction area, the dry chemical components dissolve in which part of the sample?
A) The protein fraction.
B) The lipid fraction.
C) The aqueous part.
D) The DNA strands.
Correct Answer: C
99. Chemiluminescence and Bioluminescence differ from fluorescence and phosphorescence because the excitation event is caused by:
A) A chemical or electrochemical reaction and not by photolumination.
B) High temperature.
C) UV light.
D) Magnetic fields.
Correct Answer: A
100. Oxidation of which organic compound by hydrogen peroxide in the presence of a catalyst such as microperoxidase produces a light emission used in chemiluminescence?
A) MUP.
B) Luciferase.
C) Isoluminol.
D) Phenol.
Correct Answer: C
Immunochemical Techniques (Questions 101–120)
101. The primary phase of the reaction between an antigen and antibody involves the formation of:
A) An immune precipitate.
B) A cross-linked lattice.
C) An immune complex (which scatters light).
D) Covalent bonds.
Correct Answer: C
102. Immunochemical techniques dependent on the properties of an immune complex are generally performed by using:
A) Equivalent amounts of antigen and antibody.
B) Excess antigen.
C) Excess antibody.
D) No buffer.
Correct Answer: C
103. Which types of forces are the main forces that hold the antigen-antibody complex together?
A) Covalent bonds (40 to 140 Kcal).
B) Hydrogen bonds (2 to 5 Kcal).
C) Van der Waals forces (about 0.5 Kcal).
D) Ionic bonds.
Correct Answer: C
104. The strength of binding of an antigen to the number of antibody binding sites is a measure of the antibody's:
A) Specificity.
B) Avidity.
C) Affinity constant.
D) Solubility.
Correct Answer: B
105. Immunonephelometry measures the rate of:
A) Absorption of light.
B) Decrease in incident light intensity.
C) Light-scatter formation resulting from an immunoprecipitate reaction.
D) Dissolution of the immune complex.
Correct Answer: C
106. Immunoturbidimetry involves the measurement of the decrease in intensity of the incident light beam caused by:
A) Light scatter, reflectance, and absorption of the light.
B) Fluorescence emission.
C) The dissociation rate constant.
D) The use of radioactive labels.
Correct Answer: A
107. In Radioimmunoassays (RIA), how is the ratio of bound label (B) to free label (F) related to the concentration of unlabeled antigen in the serum?
A) Directly proportional.
B) Inversely proportional.
C) Not related.
D) Linearly related.
Correct Answer: B
108. What radioactive isotope is generally used as a label material in radioimmunoassays and detected by solid scintillation gamma counters?
A) ³H.
B) ¹⁴C.
C) ¹²⁵I.
D) ³²P.
Correct Answer: C
109. What specialized device is used in a gamma counter to detect photons released when γ-rays from the radioactive label strike it?
A) Photomultiplier tube.
B) Sodium iodide crystal activated with 1% thallium.
C) Graphite brush.
D) Fiber matrix.
Correct Answer: B
110. The Immunoradiometric Assay (IRMA) is considered a direct binding assay where the antigen concentration is directly proportional to the radioactivity present. How does this differ from RIA?
A) RIA uses labeled antibody; IRMA uses labeled antigen.
B) IRMA utilizes purified radiolabeled antibody in excess, while RIA is a competitive displacement assay using limited radioactive antigen.
C) IRMA is homogeneous; RIA is heterogeneous.
D) IRMA measures UV light; RIA measures visible light.
Correct Answer: B
111. What is the widely used homogeneous enzyme immunoassay that does not require a separation step?
A) ELISA.
B) IRMA.
C) MEIA.
D) Enzyme Multiplied Immunoassay Technique (EMIT).
Correct Answer: D
112. In a homogeneous EIA, what effect does the binding of the analyte antibody with the enzyme-analyte conjugate have on the enzyme activity?
A) It increases the enzyme activity exponentially.
B) It physically blocks access of the substrate to the active site or changes the enzyme conformation, altering its activity.
C) It causes the emission of light.
D) It results in immediate precipitation.
Correct Answer: B
113. In the Indirect ELISA procedure, what component is enzyme-labeled and added after the sample containing the specific antibody has reacted with the antigen coated on the solid phase?
A) The substrate.
B) Enzyme labeled antihuman globulin.
C) Biotin-labeled antibody.
D) Fluorescein-Tracer-labeled analyte.
Correct Answer: B
114. Microparticle Enzyme Immunoassay (MEIA) uses a solution of suspended, sub-micron sized latex particles. Why are MEIA assays completed in less time than other immunoassays?
A) The system uses UV kinetics.
B) The effective surface area of microparticles increases assay kinetics and decreases assay incubation time.
C) They use high temperatures.
D) They rely on constant current coulometry.
Correct Answer: B
115. In Fluorescence Polarization Immunoassays (FPIA), what characteristic of the molecule is the average polarization of the emitted fluorescence related to?
A) The electrical charge.
B) The size of the molecule (which affects the speed of rotation in liquid).
C) The temperature stability.
D) The extinction coefficient.
Correct Answer: B
116. In FPIA, if the sample contains a high concentration of the analyte, how does this affect the binding and polarization?
A) More analyte tracer binds, resulting in increased polarization.
B) More specimen analyte binds, leaving more small unbound analyte tracer, resulting in a decrease in polarization.
C) The complex rotation slows to zero.
D) The emitted light is absorbed entirely.
Correct Answer: B
117. What two technologies does Fluorescence Polarization Immunoassay (FPIA) combine?
A) Nephelometry and Turbidimetry.
B) Electrophoresis and Densitometry.
C) Competitive protein binding and Fluorescence polarization.
D) Bioluminescence and Chemiluminescence.
Correct Answer: C
118. In Radiative Energy Attenuation (REA) assays, the light-absorbing properties of the produced chromophore cause a decrease in the measured fluorescent light intensity from what other substance included in the reaction mixture?
A) Analyte.
B) Chromogen.
C) Fluorophore (stable fluorescent substance).
D) Alkaline phosphatase.
Correct Answer: C
119. REA assays use Beer's law principle and measure the concentration of analyte based on the principle that the logarithm of measured fluorescent light intensity is inversely proportional to the amount of:
A) Analyte in the specimen.
B) Chromophore present.
C) Fluorophore remaining.
D) Enzyme label.
Correct Answer: B
120. Which principle is used to ensure the irreversible binding of microparticles to the glass fibers in the MEIA process?
A) Competitive protein binding.
B) Irreversible binding of the microparticles causes the immune complex to be retained by the glass fibers.
C) Gel filtration.
D) Electrophoresis.
Correct Answer: B
Electrophoresis, Densitometry, and Blotting (Questions 121–135)
121. The term electrophoresis describes the migration of a charged particle under the influence of:
A) Gravity.
B) Centrifugal force.
C) An electric field.
D) Viscosity of the medium.
Correct Answer: C
122. According to the electrophoretic mobility (M) equation, mobility is dependent on which key factors?
A) Applied voltage (x) and time.
B) Viscosity of the medium ($\eta$), shape and size (R) of the particle, and charge on the molecule (q).
C) Ionic strength and pH only.
D) Molecular weight and density.
Correct Answer: B
123. If the ionic strength of a buffer used in electrophoresis is increased, what effect does this have on the migration of charged particles?
A) Migration rate increases.
B) Migration rate remains constant.
C) Decrease in the migration of charged particles.
D) Particles migrate toward the anode only.
Correct Answer: C
124. At pH 8.6, all serum proteins bear a net negative charge and thus move toward which electrode?
A) Cathode (negative electrode).
B) Anode (positive electrode).
C) Neutral pole.
D) They do not move at all.
Correct Answer: B
125. How does the Freezing Point (F.P.) of a solution change as the concentration of solute particles in a specimen increases (a colligative property)?
A) F.P. increases.
B) F.P. decreases.
C) F.P. remains constant.
D) F.P. becomes zero.
Correct Answer: B
126. What phenomenon is described as the movement of buffer toward the cathode due to fixed negatively charged groups in the supporting medium (like agaropectin in agar) that impede the migration of negatively charged particles toward the anode?
A) Reverse osmosis.
B) Polymeric sieving.
C) Electroendosmosis.
D) Blotting.
Correct Answer: C
127. Which supporting medium is preferred for separating serum proteins, lipoprotein, hemoglobins, and isoenzymes due to its large pore size, transparency, and rapid electrophoresis time (30 to 120 minutes)?
A) Filter paper.
B) Agarose gel.
C) Polyacrylamide gel.
D) Nitrocellulose membrane.
Correct Answer: B
128. What property do Polyacrylamide gels possess that allows separation of various components both on the basis of molecular size and charge?
A) High electroendosmosis.
B) Molecular sieving properties.
C) Transparency.
D) Minimal adsorption.
Correct Answer: B
129. What technique involves incorporating Sodium Dodecyl Sulfate (SDS) with the sample to dissociate proteins into their subunit polypeptide chains, which are then separated based on molecular weight?
A) Polyacrylamide Gel Electrophoresis (PAGE).
B) SDS - polyacrylamide gel electrophoresis.
C) Double diffusion.
D) Radial immunodiffusion.
Correct Answer: B
130. A densitometer is essentially a double beam filter photometer or spectrophotometer that scans the electrophoretic strip and computes the area under each graphical peak using what component?
A) A monochromator.
B) An electronic integrator.
C) A magnetic stirrer.
D) A flow cell.
Correct Answer: B
131. Which blotting technique involves the electrophoretic separation of proteins, followed by transfer to a solid support for subsequent detection?
A) Southern blotting.
B) Northern blotting.
C) Western blotting.
D) Southwestern blotting.
Correct Answer: C
132. Southern blot techniques assay which test material?
A) RNA.
B) Protein.
C) DNA.
D) Lipids.
Correct Answer: C
133. In the Western blot example for HIV-1 antibody detection, what forms a complex with the bound HIV-1 antibody after washing?
A) A specific substrate.
B) An alkaline phosphatase - antihuman immunoglobulin conjugate.
C) A radiolabeled probe.
D) A biotin-labeled antibody.
Correct Answer: B
134. Northern blotting assays which test nucleic acid?
A) DNA.
B) RNA.
C) Protein.
D) Peptide.
Correct Answer: B
135. What is the limit of detection for antigen concentration per band in a gel using the protein transfer and immobilization technique described, which can be lowered using chemiluminescent assays?
A) As low as 500 ng/ml or 2.5 ng per band in the gel.
B) 100 mg/dl.
C) 1.0 g/dl.
D) 10 pg.
Correct Answer: A
136. Chromatography is a technique that separates components by continuous distribution and redistribution between two phases: one stationary and the other:
A) Insoluble.
B) Aqueous.
C) Mobile.
D) Gaseous only.
Correct Answer: C
137. Coulometry is a technique used to determine which specific ion in a specimen, based on constant-current coulometry?
A) Sodium ions.
B) Chloride ions.
C) Hydrogen ions.
D) Potassium ions.
Correct Answer: B
138. In Ion-exchange chromatography, separation of constituents is based on:
A) Size difference.
B) Solubility.
C) The number and types of charges present on the ion-exchange resin column.
D) Adsorption to an inorganic material.
Correct Answer: C
139. How are molecules separated in Gel filtration chromatography?
A) On the basis of their difference in size.
B) On the basis of their partition coefficient.
C) On the basis of their electrical charge.
D) On the basis of their affinity to the solid phase.
Correct Answer: A
140. In Gel filtration, which molecules leave the column first?
A) Small molecules, which diffuse into the gel.
B) Large molecules, which are excluded from the cross-linked network and follow a shorter path.
C) Molecules with a partition coefficient K > 1.
D) Charged molecules.
Correct Answer: B
141. What type of chromatography uses a liquid-liquid system in which one liquid acts as a stationary liquid phase supported by cellulose fibers of a paper sheet?
A) Thin-layer chromatography (TLC).
B) High-Performance Liquid Chromatography (HPLC).
C) Adsorption chromatography.
D) Paper Chromatography.
Correct Answer: D
142. What characteristics of the packing material are utilized in HPLC to achieve high performance compared to traditional liquid chromatography?
A) Large particle size (50 to 100 $\mu$m).
B) Packing materials of small particle size (5 to 20 $\mu$m).
C) High resistance to solvent flow.
D) Gravity feed solvent delivery.
Correct Answer: B
143. What is the mode of HPLC operation when the mobile phase composition remains constant throughout the chromatography run?
A) Gradient mode.
B) Isocratic mode.
C) Reversed phase mode.
D) Ion-exchange mode.
Correct Answer: B
144. What material is commonly used as a stationary support for HPLC columns?
A) Filter paper.
B) Agarose gel.
C) Silica, alumina, charcoal, and organic polymers.
D) High-pressure hydrogen.
Correct Answer: C
145. What types of detectors are commonly used in HPLC systems?
A) Gamma counters.
B) Ultraviolet light, visible light, and diode array absorbance detectors.
C) Photomultiplier tubes only.
D) pH electrodes.
Correct Answer: B
DNA Probes and PCR (Questions 146–160)
146. In DNA structure, Adenine on one chain forms how many hydrogen bonds with its complementary base Thymine on the opposite strand?
A) One.
B) Two.
C) Three.
D) Four.
Correct Answer: B
147. What is the process called when two complementary strands of DNA recombine to form a stable duplex molecule after being separated by a denaturing agent?
A) Polymerase Chain Reaction (PCR).
B) Fragmentation.
C) Annealing or hybridization.
D) Transcription.
Correct Answer: C
148. What is a short, relatively well-characterized segment of nucleic acid, often labeled, used to search an unknown sample for complementary sequences through hybridization?
A) Restriction enzyme.
B) Template.
C) Nucleic acid probe.
D) Plasmid.
Correct Answer: C
149. What is the main objective of Polymerase Chain Reaction (PCR)?
A) To fragment DNA using restriction enzymes.
B) To sequence DNA nucleotides.
C) To generate sufficient quantities of DNA by increasing (amplifying) the number of copies of the target region.
D) To separate proteins based on size.
Correct Answer: C
150. In PCR methodology, what is the required temperature for the step known as 'Annealing the primers to the DNA'?
A) 94°C.
B) 72°C.
C) 60°C.
D) 37°C.
Correct Answer: C
151. What is the primary characteristic required for the DNA polymerase enzyme used in PCR?
A) It must be derived from yeast.
B) It must be thermostable.
C) It must only function at 37°C.
D) It must be able to cleave blunt ends.
Correct Answer: B
152. Approximately how many cycles of PCR are required to produce a million-fold amplification of ds DNA?
A) 5 cycles.
B) 10 cycles.
C) 20 cycles.
D) 50 cycles.
Correct Answer: C
153. What is the purpose of adding EDTA to the saline solution during the DNA extraction process for PCR?
A) To denature proteins.
B) To facilitate cell rupture.
C) To chelate metal ions needed for DNase and inhibit its activity.
D) To separate the DNA strands.
Correct Answer: C
154. Which enzyme is used in the Reverse Transcriptase-PCR (RT-PCR) technique to convert mRNA to complementary DNA (cDNA)?
A) Restriction endonuclease.
B) DNA ligase.
C) Reverse transcriptase.
D) Taq polymerase.
Correct Answer: C
155. What type of enzymes are widespread in bacteria and serve a defensive function by cleaving molecules of foreign DNA at specific nucleotide sequences?
A) Polymerases.
B) Ligases.
C) Restriction endonucleases.
D) Transferases.
Correct Answer: C
156. In the radioactive labeling of cDNA by nick translation, which radioactive isotope is most frequently used?
A) Carbon - 14
B) Iodine - 125
C) Phosphorus - 32
D) Tritium - 3
Correct Answer: C
157. What substance binds with extremely high avidity to small molecular biotin (Vitamin H), and can be linked with an enzyme or fluorescent tag for non-radioactive probe detection?
A) Agarose.
B) Avidin.
C) Riboflavin.
D) Nitrocellulose.
Correct Answer: B
158. In the preparation of a recombinant plasmid for gene cloning, what enzyme is used to anneal DNA fragments with complementary sticky ends of the plasmid?
A) Restriction endonuclease.
B) Reverse transcriptase.
C) DNA ligase.
D) Terminal transferase.
Correct Answer: C
159. What specific mutation is mentioned as the lesion in β-thalassemia?
A) Glutamic acid codon GAG is mutated to valine codon GTG.
B) The glutamine codon CAG is mutated to stop codon TAG.
C) A mutation in the poly(A) tail.
D) A deletion of the poly(dT) primer sequence.
Correct Answer: B
160. What technique detects variation in the length of fragments obtained by restriction endonuclease treatment and is useful when the exact genetic sequence related to a disorder is unknown?
A) Fluorescence Polarization Immunoassay (FPIA).
B) Restriction Fragment Length Polymorphism (RFLP).
C) Southern Blotting.
D) Microparticle Enzyme Immunoassay (MEIA).
Correct Answer: B
161. The most reliable and convenient method for measuring pH is by the use of a pH meter, which measures the e.m.f. of a concentration cell formed from a reference electrode (e.g., Calomel electrode), the test solution, and what other key component?
A) A salt bridge.
B) A galvanometer.
C) A glass electrode.
D) A potentiometric detector.
Correct Answer: C
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